Air precleaners that separate heavier-than-air particles from the air used in combustion type engines are known. One example of a prior art air precleaner, a scavenger based system for a combustion type engine is shown in FIG. 1 wherein air precleaner 1 for combustion type engine 2 comprises an air inlet 3 through which debris-laden-air is drawn from the atmosphere by a vacuum. The vacuum is applied by the intake of the engine which is connected to the outlet of the air precleaner through an air filter housing 4. The air inlet contains fixed vanes for rotating the debris-laden-air drawn into the air precleaner to centrifugally separate debris which is collected in a dust ejector body 5 in a catch tray. A vacuum from the exhaust gas flow from the engine in muffler 6 is used to scavenge the collected debris from the catch tray in the ejector body via a crossover tube 7 connected to a scavenger port in ejector body adjacent the catch tray.
The needs of current combustion engine designs for extremely low initial restriction and high particle separating efficiency over the broad airflow range with which they are used was addressed by the invention of the air precleaner, 8 in FIG. 2, of assignee's U.S. Pat. Nos. 5,656,050 and 5,766,315, the disclosures of which are hereby incorporated by reference. As depicted in FIG. 2, the air precleaner 8 is an ejective based system in which debris laden air enters, see arrow A, through recessed vanes 9 in the bottom of the precleaner. A curved particle accelerator 10 in a separator chamber 11 of the precleaner rotates much faster than the incoming air. Debris is captured and passed down the length of the particle accelerator's straked appendages. Debris is then deposited on an inner wall 12 of the separator chamber. The particle accelerator spins deposited debris toward an ejection duct 13 in the separator chamber where it is ejected from the vortex, e.g. rotating flow in the separator chamber. Clean air continues to spin upwardly until it is redirected and compressed into an air outlet opening in the center of the bottom of the precleaner.
The air precleaner of FIG. 2 offers improved performance compared with that in FIG. 1. However, it has been found that in extreme conditions, such as found in many landfill and transfer station operations, the known precleaners may fail to provide satisfactory performance. The present invention solves this problem by combining the benefits of both ejective and scavenger based systems to achieve outstanding performance and substantial improvement in air filter life when operating under these extreme conditions.
An air precleaner of the invention for separating heavier-than-air particulate debris from debris laden air to provide a clean airflow, comprises:
a flow path extending through the precleaner from inlet to an outlet;
airflow management structure positioned to direct debris laden air drawn into the precleaner into a vortex flow in the flow path;
a first stage, ejective based precleaner in the flow path to centrifugally separate and remove particles of debris from the vortex path, the first stage precleaner including a particle accelerator rotatably mounted in the first stage precleaner to increase the rotational velocity of the vortex flow and encourage removal of debris therefrom; and
a second stage, scavenger based precleaner in the flow path downstream from the first stage precleaner to centrifugally separate and remove from the vortex flow particles of debris remaining in the vortex flow. This dual stage air precleaner of the invention has been found to increase air filter life under extreme conditions ten times as compared with the use of single stage air precleaners.
A method of separating heavier-than-air particulate debris from debris laden air to provide a clean air flow according to the invention comprises:
drawing debris laden air into an inlet of an air cleaning system by application of a vacuum to an outlet of the air cleaning system which is in communication with the inlet by way of a flow path extending through the system;
directing debris laden air drawn into the inlet of the air cleaning system into a vortex flow in the flow path;
centrifugally separating and removing particles of debris from the vortex flow in a separator chamber of a first stage, ejective based precleaner of the system, wherein the centrifugal separating and removing is facilitated by transferring energy from the vortex flow in the flow path downstream of the separator chamber of the first stage precleaner to increase the rotational velocity of the vortex flow in the separator chamber of the first stage precleaner; and
centrifugally separating and removing remaining particles of debris from the vortex flow at a second stage, scavenger based precleaner in the flow path downstream of the first stage precleaner.
These and other objects, features and advantages of the present invention will become more apparent from the following description of an example embodiment in accordance with the invention when taken in connection with the accompanying drawings.